Gradient magnetic field generation module using plurality of coils so as to generate gradient magnetic field

ABSTRACT

Provided is a gradient magnetic field generation module using multiple coils to generate a gradient magnetic field. Provided is a gradient magnetic field generation module including: a gradient coil formed inside a main magnet and generating a gradient magnetic field and including a plurality of coils; and a gradient amplifier controlling at least one of a shape of the gradient magnetic field, a strength of the gradient magnetic field, and slew rate of the gradient magnetic field generated by the gradient coil, in which the plurality of coils is grouped into a plurality of coil groups and current which flows in the plurality of coils is independently controlled by the unit of a group by the gradient amplifier.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/KR2016/005160, filed on May 16, 2016, which claims the benefitof U.S. Provisional Patent Application Ser. No. 62/164,896, filed on May21, 2015, each of which is hereby incorporated by reference in itsentirety herein.

TECHNICAL FIELD

The present disclosure relates to a gradient magnetic field generationmodule, and particularly, to a module for generating various gradientmagnetic fields.

BACKGROUND ART

Magnetic resonance imaging (MRI) provides information obtained throughresonance after exposing an atomic nucleus to a magnetic field as animage. The resonance of the atomic nucleus refers to a phenomenon inwhich when a specific high frequency is incident in the atomic nucleusmagnetized by an external magnetic field, the atomic nucleus in a lowenergy state is excited to a high energy state by absorbing highfrequency energy. The atomic nuclei have different resonance frequenciesdepending on a type and the resonance is influenced by an intensity ofan external magnetic field. There are innumerable atomic nuclei inside ahuman body and hydrogen atomic nuclei are generally used forphotographing a magnetic resonance image.

A magnetic resonance imaging system may generate a gradient magneticfield in a magnetic resonance imaging apparatus. The generated gradientmagnetic field may be used to create a section of a region to bephotographed. In a method for generating the gradient magnetic field inthe related art, a uniform gradient magnetic field cannot be generated,and as a result, there is inconvenience.

Accordingly, a method for generating various gradient magnetic fields inthe magnetic resonance imaging system is being studied.

A prior art document related to the method is Patent Registration No. KR10-1503494.

SUMMARY

The present disclosure discloses methods and systems for efficientlygenerating various gradient magnetic fields.

As a technical means for achieving the technical object, a first aspectof the present disclosure may provide a gradient magnetic fieldgeneration module including: a gradient coil formed inside a main magnetand generating a gradient magnetic field and including a plurality ofcoils; and a gradient amplifier controlling at least one of a shape ofthe gradient magnetic field, a strength of the gradient magnetic field,and a slew rate of the gradient magnetic field generated by the gradientcoil, in which the plurality of coils is grouped into a plurality ofcoil groups and current which flows in the plurality of coils isindependently controlled by the unit of a group and by the gradientamplifier.

The present disclosure can provide a method for generating variousgradient magnetic fields.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects are now described with reference to the drawings andlike reference numerals are generally used to designate like elements.In the following embodiments, for a description purpose, multiplespecific detailed matters are presented to provide general understandingof one or more aspects. However, it will be apparent that the aspect(s)can be executed without the detailed matters. In other examples, knownstructures and apparatuses are illustrated in a block diagram form inorder to facilitate description of the one or more aspects.

FIG. 1 is a block diagram illustrating a magnetic resonance imagingapparatus according to an embodiment of the present disclosure.

FIGS. 2A, 2B, and 2C illustrate a structure of a gradient coil accordingto an embodiment of the present disclosure.

FIG. 3 is a diagram for describing a Z-axis gradient coil according toan embodiment of the present disclosure.

FIG. 4 is a diagram for describing an operation of a gradient amplifieraccording to an embodiment of the present disclosure.

FIG. 5 is a diagram for describing an operation of a gradient amplifieraccording to another embodiment of the present disclosure.

FIG. 6 is a circuit diagram for describing the gradient amplifieraccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Various embodiments will now be described with reference to drawings andlike reference numerals are used to refer to like elements throughoutall drawings. In the present specification, various descriptions arepresented to provide appreciation of the present disclosure. However, itis apparent that the embodiments can be executed without the specificdescription. In other examples, known structures and apparatuses arepresented in a block diagram form in order to facilitate description ofthe embodiments.

Terms used in the present specification will be described in brief andthe present disclosure will be described in detail. Terms used in thepresent disclosure adopt general terms which are currently widely usedas possible by considering functions in the present disclosure, but theterms may be changed depending on an intention of those skilled in theart, a precedent, emergence of new technology, etc. Further, in aspecific case, a term which an applicant arbitrarily selects is presentand in this case, a meaning of the term will be disclosed in detail in acorresponding description part of the invention. Accordingly, a termused in the present disclosure should be defined based on not just aname of the term but a meaning of the term and contents throughout thepresent disclosure.

Further, throughout the specification, unless explicitly described tothe contrary, the word “comprise” and variations such as “comprises” or“comprising”, will be understood to imply the inclusion of statedelements but not the exclusion of any other elements.

Further, the term “unit” or “module” used in the specification meanssoftware and hardware components and the “unit” or “module” performspredetermined roles. However, the “unit” or “module” is not a meaninglimited to software or hardware. The “unit” or “module” may beconfigured to reside on an addressable storage medium and may beconfigured to play back one or more processors.

Accordingly, as one example, the “unit” or “module” includes componentssuch as software components, object oriented software components, classcomponents, and task components, processes, functions, attributes,procedures, subroutines, segments of a program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. Functions provided in the components and the “units” or“modules” may be combined into a smaller number of components and“units” or “modules” or further separated into additional components and“units” or “modules”.

An embodiment of the present disclosure will be described more fullyhereinafter with reference to the accompanying drawings so as to beeasily implemented by those skilled in the art. In addition, a partwhich is not related with the description is omitted in the drawings inorder to clearly describe the present disclosure.

In the present specification, “image” may mean multi-dimensional dataconstituted by discrete image elements (e.g., pixels in a 2D image andvoxels in a 3D image). For example, the image may include a medicalimage of an object, which are acquired by X-ray, CT, MRI, ultrasonicwaves, and other medical imaging systems, and the like. Further, in thepresent specification, the “object” may include a person or an animal,or a part of the person or the animal. For example, the object mayinclude organs including liver, heart, uterus, brain, breast, abdomen,and the like or a blood vessel. Further, the “object” may include aphantom. The phantom means a material that has a density of a livingthing and a volume that is very proximate to an effective atomic numberand can include a spherical phantom that has a similar property to ahuman body.

Further, in the present specification, a “user” as a medical specialistmay be a doctor, a nurse, a medical technologist, a medical imagingexpert, or the like and be a technician repairing a medical apparatus,but is not limited thereto.

Further, in the present specification, the term “magnetic resonanceimaging (Mill)” means an image for an object obtained using a nuclearmagnetic resonance principle.

In addition, in the present specification, the term “pulse sequence”means a series of signals repeatedly applied in the MRI apparatus. Thepulse sequence may include a time parameter of an RF pulse, for example,a repetition time (TR) and a time to echo (TE).

Further, in the present specification, the term “TR” may mean therepetition time of the RF pulse. For example, the TR may mean a timebetween a transmission time of a first RF pulse and a transmission timeof a second RF pulse.

Further, in the present specification, the term “pulse sequenceschematic diagram” denotes an order in which the signals are applied inthe MRI apparatus. For example, the pulse sequence schematic diagram maybe a schematic diagram illustrating the RF pulse, a gradient magneticfield, a magnetic resonance signal, etc., with time.

Further, in the present specification, the term “spatial encoding”refers to obtaining spatial information along an axis (direction) of thegradient magnetic field by applying a linear gradient magnetic fieldthat causes additional dephasing of a proton spindle in addition todephasing of the proton spindle by an RF signal.

The MRI apparatus is an apparatus for acquiring an image of asingle-layer portion of the object by expressing the intensity of amagnetic resonance (MR) signal for a radio frequency (RF) signalgenerated in a magnetic field of a specific intensity in contrast. Forexample, when the object is laid in a strong magnetic field andthereafter, the RF signal to resonate only a specific atomic nucleus(e.g., a hydrogen atomic nucleus, etc.) is irradiated to the object andstopped, the magnetic resonance signal is emitted from the specificatomic nucleus and the MRI apparatus may obtain an MR image by receivingthe magnetic resonance signal. The magnetic resonance signal refers tothe RF signal irradiated from the object. The magnitude of the magneticresonance signal may be determined by the concentration of predeterminedatoms (e.g., hydrogen, etc.) contained in the object, a relaxation timeT1, a relaxation time T2, and a flow of a bloodstream.

The MRI apparatus includes features different from other imagingapparatuses. Unlike imaging apparatuses, such as CT, where acquisitionof an image is dependent on a direction of detecting hardware, the MRIapparatus may acquire a two-dimensional image or a three-dimensionalvolume image directed to any point. Further, unlike CT, X-ray, PET, andSPECT, the MRI apparatus does not expose the object and an examinee toradiation, and may acquire an image having a high soft tissue contrast.Therefore, a neurological image, an intravascular image, amusculoskeletal image, and an oncologic image in which it is importantto clearly describe abnormal tissue may be obtained.

A three-dimensional volume of the object may include a three-dimensionalshape of a person or animal, or a part of the person or the animal. Forexample, the volume of the object may include the three-dimensionalshape of organs including liver, heart, uterus, brain, breast, abdomen,and the like or a blood vessel, etc.

When the MRI apparatus intends to acquire information of the 3D volumeof the object in a short time, it is possible to acquire a plurality ofsheets of slice images in the direction of the slices constituting the3D volume. When images of a plurality of slices are photographed, it iscommon to sequentially photograph the slice images as many as theslices, but taking the slice images sequentially may require a lot ofphotographing time.

In a multi-slice scheme, when each slice image is acquired in aplurality of repetition time (TR) intervals, data for each slice isacquired in each TR interval in a cross direction to shorten aphotographing time. For example, there is a dead time when the TRinterval is much longer than an active time required for cross-sectionselection, phase encoding, and frequency encoding. In the multi-slicescheme, in order to obtain information on another cross section afterobtaining information on one cross section in each TR interval, the deadtime may be used.

In a simultaneous multi-slice (SMS) scheme, the plurality of slices issimultaneously excited to reduce a scan time to simultaneously acquirethe magnetic resonance signals from the plurality of slices through aplurality of coils and a difference in coil sensitivity informationwhich exists between the slices is used to separate the magneticresonance signals for each slice. The coil sensitivity information maymean a sensitivity to receive different magnetic resonance signalsdepending on a location of each coil among the plurality of coils.

The simultaneous multi-slice scheme may correspond to parallel imaging,and the parallel imaging may include a sense scheme or a GRAPPA scheme.

FIG. 1 is a block diagram illustrating a magnetic resonance imagingapparatus according to an embodiment of the present disclosure.

Referring to FIG. 1, a magnetic resonance imaging apparatus may includea gantry 20, a signal transceiving unit 30, a monitoring unit 40, adevice control unit 50, and an operating unit 60.

The gantry 20 may block electromagnetic waves generated by a main magnet22, a gradient coil 24, an RF coil 26, etc. from being radiated to theoutside. The gantry 20 may include a bore therein. An electromagneticfield and a gradient magnetic field may be formed in the bore and an RFsignal may be irradiated from the bore toward an object 10.

The main magnet 22, the gradient coil 24, and the RF coil 26 may bedisposed in a predetermined direction of the gantry 20. Thepredetermined direction may include a coaxial cylindrical direction,etc. The object 10 may be positioned on a table 28 insertable into acylinder along a horizontal axis of the cylinder.

The main magnet 22 may generate a static magnetic field for aligning amagnetic dipole moment of the atomic nuclei included in the object 10 ina predetermined direction.

As the magnetic field generated by the main magnet is stronger and moreuniform, a relatively precise and accurate MR image with respect to theobject 10 may be obtained.

According to the embodiment of the present disclosure, a magneticresonance circuit system may include a gradient magnetic fieldgeneration module. The gradient magnetic field generation module means amodule which generates the gradient magnetic field to form a gradientmagnetic field. The gradient magnetic field generation module mayinclude a gradient amplifier 32 and a gradient magnetic field coil 24.

The gradient amplifier 32 can apply the current to the gradient magneticfield coil 24 under the control of a gradient magnetic field controlunit 54. In this case, the gradient amplifier 32 may supply the currentto the gradient magnetic field coil 24 for a predetermined time and stopsupplying the current when the predetermined time has elapsed.

According to the embodiment of the present disclosure, the gradientamplifier 32 applies various currents to the coil group under thecontrol of the gradient magnetic field control unit 54 to generategradient magnetic fields having various magnitudes and directions. Forexample, the gradient amplifier 32 applies the current to the coil groupto control at least one of a shape of the gradient magnetic field, thestrength of the gradient magnetic field, and a slew rate of the gradientmagnetic field generated by the coil group.

The gradient coil 24 may include X, Y, and Z coils that generate agradient magnetic field in mutually orthogonal X-, Y-, and Z-axisdirections. The gradient coil 24 may provide positional information ofeach part of the object 10 by inducing resonance frequencies differentlyfor each part of the object 10.

The RF coil 26 may irradiate RF signals to a patient and receivemagnetic resonance signals emitted from the patient. For example, the RFcoil 26 may transmit an RF signal having a frequency equal to afrequency of a processional motion toward the atomic nucleus whichperforms the processional motion and thereafter, stop transmission ofthe RF signal and receive the magnetic resonance signal emitted from thepatient.

For example, the RF coil 26 may generate an electromagnetic signal,having a radio frequency corresponding to the type of atomic nucleus,for example, an RF signal, and apply the generated RF signal to theobject 10 so as to transition a certain atomic nucleus from a low energystate to a high energy state. When the electromagnetic signal generatedby the RF coil 26 is applied to the certain atomic nucleus, the certainatomic nucleus may transition from the low energy state to the highenergy state. Thereafter, when the electromagnetic wave generated by theRF coil 26 is removed, the atomic nucleus to which the electromagneticwave has been applied may emit electromagnetic waves having a Larmorfrequency while transiting from the high energy state to the low energystate. In other words, when the application of the electromagneticsignal to the atomic nucleus is interrupted, while an energy level fromhigh energy to low energy is changed in the atomic nucleus to which theelectromagnetic wave is applied is changed, the electromagnetic wavehaving the Larmor frequency may be emitted. Here, the Larmor frequencymay mean a frequency at which magnetic resonance is induced in theatomic nucleus.

The RF coil 26 may receive the electromagnetic signals irradiated fromthe atomic nuclei inside the object 10. The RF coil 26 may beimplemented as one RF transceiving coil having both a function ofgenerating the electromagnetic wave having the radio frequencycorresponding to the type of atomic nucleus and a function of receivingthe electromagnetic waves irradiated from the atomic nucleus.

Further, the RF coil 26 may be implemented as each of a transmission RFcoil having the function of generating the electromagnetic wave havingthe radio frequency corresponding to the type of atomic nucleus and areception RF coil having the function of receiving the electromagneticwave irradiated from the atomic nucleus.

Further, the RF coil 26 may be fixed to the gantry 20 and may beremovable. The removable RF coil 26 may include RF coils for a portionof the object including a head RF coil, a thorax RF coil, a leg RF coil,a neck RF coil, a shoulder RF coil, a wrist RF coil, and an ankle RFcoil.

Further, the RF coil 26 may communicate with an external device by awired and/or wireless manner and may perform even dual tunecommunication according to a communication frequency band.

In addition, the RF coil 26 may include a birdcage coil, a surface coil,and a transverse electromagnetic coil (TEM coil) according to astructure of the coil.

In addition, the RF coil 26 may include a transmission-only coil, areception-only coil, and a transmission/reception-combination coilaccording to a method of transceiving the RF signal.

Further, the RF coil 26 may include RF coils of various channels such as16 channels, 32 channels, 72 channels, and 144 channels.

The gantry 20 may further include a display 29 positioned outside thegantry 20 and a display (not illustrated) positioned inside the gantry20. Predetermined information may be provided to the user or the objectvia the displays positioned inside and outside of the gantry 20.

The signal transceiving unit 30 may control a gradient magnetic fieldformed in the gantry 20 according to a predetermined MR sequence andcontrol transmission and reception of the RF signal and the magneticresonance signal.

The signal transceiving unit 30 may include a gradient amplifier 32, atransceiving switch 34, an RF transmitting unit 36, and an RF receivingunit 38.

The gradient amplifier 32 may drive the gradient coil 24 included in thegantry 20 and supply a pulse signal for generating the gradient magneticfield to the gradient coil 24 under the control of the gradient magneticfield control unit 54.

The gradient magnetic field control unit 54 may control the pulse signalsupplied from the gradient amplifier 32 to the gradient coil 24. Bycontrolling the pulse signal supplied to the gradient coil 24, thegradient magnetic fields in X-axis, Y-axis, and Z-axis directions may besynthesized. The pulse signal may be implemented by current.

The RF transmitting unit 36 and the RF receiving unit 38 may drive theRF coil 26. The RF transmitting unit 36 may supply the RF pulse of theLarmor frequency to the RF coil 26 and the RF receiving unit 38 mayreceive the magnetic resonance signal received by the RF coil 26.

The transceiving switch 34 may adjust transmission/reception directionsof the RF signal and the magnetic resonance signal. For example, thetransceiving switch 34 may cause the RF signal to be irradiated to theobject 10 through the RF coil 26 during a transmission mode and themagnetic resonance signal from the object 10 through the RF coil 26 tobe received during a reception mode. The transceiving switch 34 may becontrolled by a control signal from an RF control unit 56.

The monitoring unit 40 may monitor or control the gantry 20 or devicesmounted on the gantry 20. The monitoring unit 40 may include a systemmonitoring unit 42, an object monitoring unit 44, a table control unit46, and a display control unit 48.

The system monitoring unit 42 may monitor and control a state of thestatic magnetic field, the state of the gradient magnetic field, thestate of the RF signal, the state of the RF coil, the state of a table,the state of a device for measuring body information of the object, apower supply state, the state of a heat exchanger, the state of acompressor, and the like.

The object monitoring unit 44 may monitor the state of the object 10.For example, the object monitoring unit 44 may include a camera forobserving a motion or a position of the object 10, a respirationmeasurer unit for measuring respiration of the object 10, an ECGmeasurer for measuring an electrocardiogram of the object 10, or a bodytemperature measurer for measuring a body temperature of the object 10.

The table control unit 46 may control movement of the table 28 at whichthe object 10 is positioned. The table control unit 46 may control themovement of the table 28 according to sequence control of the sequencecontrol unit 50. For example, in moving imaging of the object, the tablecontrol unit 46 may continuously or intermittently move the table 28according to the sequence control by the sequence control unit 50 tothereby photograph the object in a field of view (FOV) larger than theFOV of the gantry.

The display control unit 48 may control the displays positioned outsideand inside the gantry 20. For example, the display control unit 48 maycontrol on/off of the displays positioned outside and inside the gantry20 or a screen to be output to the display, etc. Further, when a speakeris positioned inside or outside the gantry 20, the display control unit48 may control the on/off of the speaker or a sound to be output throughthe speaker, etc.

The system control unit 50 may include a sequence control unit 52 forcontrolling a sequence of signals formed in the gantry 20 and a gantrycontrol unit 58 for controlling the devices mounted on the gantry 20.

The sequence control unit 52 may include the gradient magnetic fieldcontrol unit 54 for controlling the gradient amplifier 32 and the RFcontrol unit 56. The RF control unit 56 may control the RF transmittingunit 36, the RF receiving unit 38, and the transceiving switch 34.

The sequence control unit 52 may control the gradient amplifier 32, theRF transmitting unit 36, the RF receiving unit 38, and the transceivingswitch 34 according to a pulse sequence received from the operating unit60.

Here, the pulse sequence may include all information required forcontrolling the gradient amplifier 32, the RF transmitting unit 36, theRF receiving unit 38, and the transceiving switch 34 and may include,for example, information on the intensity, an application time, anapplication timing, and the like of the pulse signal applied to thegradient coil 24.

The operating unit 60 may instruct the pulse sequence information to thesystem control unit 50 and control an operation of the entire MRIapparatus.

The operating unit 60 may include an image processing unit 62 forprocessing the magnetic resonance signal received from the RF receivingunit 38, an output unit 64, and an input unit 66.

The image processing unit 62 processes the magnetic resonance signalreceived from the RF receiving unit 38 to generate magnetic resonanceimage data for the object 10.

The image processing unit 62 may perform various signal processing suchas amplification, frequency conversion, phase detection, low frequencyamplification, filtering, and the like on the magnetic resonance signalreceived by the RF receiving unit 38.

The image processing unit 62, for example, arranges digital data ink-space data (also referred to as, for example, a Fourier space or afrequency space) of a memory and performs two-dimensional orthree-dimensional Fourier transformation of the data to reconfigure thedata into image data.

Further, the image processing unit 62 may perform synthesis processingor difference arithmetic processing of the image data as necessary.

The synthesis processing may include addition processing for a pixel,maximum value projection (MW) processing, and the like. Further, theimage processing unit 62 may store not only the reconfigured image databut also the image data subjected to the synthesis processing or thedifference arithmetic processing in a memory (not illustrated) or anexternal server.

In addition, various signal processing applied to the magnetic resonancesignal by the image processing unit 62 may be performed in parallel. Forexample, a plurality of magnetic resonance signals may be reconfiguredinto the image data by applying signal processing in parallel to theplurality of magnetic resonance signals received by a multi-channel RFcoil.

The output unit 64 may output the image data or the reconfigured imagedata generated by the image processing unit 62 to the user. In addition,the output unit 64 may output information required for the user tooperate the MRI apparatus, such as a UI (user interface), userinformation, or object information.

The output unit 64 may include the speaker, a printer, a CRT display, anLCD display, a PDP display, an OLED display, an FED display, an LEDdisplay, a VFD display, a DLP display, a PFD display, a 3D display, atransparent display, and the like and may include a variety of outputdevices within other scopes which are apparent to those skilled in theart.

The user may input object information, parameter information, a scancondition, the pulse sequence, information on image synthesis andcalculation of difference, and the like using the input unit 66. Theinput unit 66 may include a keyboard, a mouse, a trackball, a voicerecognition unit, a gesture recognition unit, a touch screen, and thelike and may include various input devices within the other scopes whichare apparent to those skilled in the art.

FIG. 1 illustrates the signal transceiving unit 30, the monitoring unit40, the system control unit 50, and the operating unit 60 as separateobjects, but those skilled in the art will be able to sufficientlyappreciate that functions performed by the signal transceiving unit 30,the monitoring unit 40, the system control unit 50, and the operatingunit 60, respectively may be performed in different objects. Forexample, it is described above that the image processing unit 62converts the magnetic resonance signal received by the RF receiving unit38 into a digital signal, but the conversion into the digital signal maybe autonomously performed by the RF receiving unit 38 or the RF coil 26.

The gantry 20, the RF coil 26, the signal transceiving unit 30, themonitoring unit 40, the system control unit 50, and the operating unit60 may be connected to each other wirelessly or by wire and may furtherinclude a device (not illustrated) for synchronizing clocks with eachother when the gantry 20, the RF coil 26, the signal transceiving unit30, the monitoring unit 40, the system control unit 50, and theoperating unit 60 are connected to each other wirelessly.

As communication among the gantry 20, the RF coil 26, the signaltransceiving unit 30, the monitoring unit 40, the system control unit50, and the operating unit 60, a high-speed digital interface such aslow voltage differential signaling (LVDS), or the like, asynchronousserial communication such as universal asynchronous receiver transmitter(UART), false synchronization serial communication, a low-latency typenetwork protocol such as a controller area network (CAN), or the like,an optical communication, or the like may be used and variouscommunication methods may be used in the scope which is apparent tothose skilled in the art.

FIGS. 2A, 2B, and 2C illustrate a structure of a gradient coil accordingto an embodiment of the present disclosure.

According to an embodiment of the present disclosure, a magneticresonance system 1000 may include a gradient magnetic field generationmodule. The gradient magnetic field generation module may be defined asa module for forming the gradient magnetic field by generating thegradient magnetic field. The gradient magnetic field generation modulemay include the gradient amplifier 32 and the gradient magnetic fieldcoil 24.

According to an embodiment of the present disclosure, the gradient coil24 changes the intensity of the main magnetic field by the main magnet22 to make a temporary gradient magnetic field. The magnetic resonanceimaging system 100 may acquire positional information of an atomicnucleus by using the generated gradient magnetic field.

The gradient coil 24 may include an X-axis gradient coil, a Y-axisgradient coil, and a Z-axis gradient coil, but is not limited thereto.

When current flows onto the Z-axis gradient coil 245 for a predeterminedtime, the strength of the magnetic field may further increase in amagnetic field direction having the same polarity as a magnetic fieldmade by the Z-axis gradient coil 245. In addition, the strength of themagnetic field may be reduced by the Z-axis gradient coil 245 whichmakes an inverse polarity to the main magnetic field. As a result, thegradient magnetic field may be generated. In this case, a resonancefrequency may be changed to be larger or smaller depending on thestrength of the gradient magnetic field.

When the Z-axis gradient coil 245 generates resonance in a specificfragment selected as a Z axis, if the current is applied to the Y-axisgradient coil 243 of the specific fragment for a predetermined time, theresonance frequency may vary according to the position of a Y axis whilethe current flows. Further, when the current is removed, the resonancefrequency may be changed to an original frequency again.

However, even though the resonance frequencies of the atomic nucleiexperiencing magnetic fields having different strengths along the Y axisbecome constant again, the atomic nuclei rotate in a state where amagnitude of a rotation phase is changed according to the position ofthe Y axis. In other words, even though a rotation frequency of theatomic nucleus is constant, the atomic nucleus is changed in phase valueaccording to the position, such as an atomic nucleus which rotates at afast position, an atomic nucleus which rotates at a slow position, orthe like. This is called phase encoding.

In the case where the current is applied to the X-axis gradient coil 241for a moment when a signal is generated while in a cross sectionselected as the Z axis is phase-encoded, the rotation frequency may bechanged along the X axis (for example, frequency encoding) and a signalcombined with a plurality of frequencies may be generated according tothe position of the atomic nucleus. The magnetic resonance imagingsystem may acquire the position of the X axis using the signal combinedwith the plurality of frequencies.

FIG. 2A is a diagram illustrating the X-axis gradient coil 241 accordingto an embodiment of the present disclosure. When the current flows inthe X-axis gradient coil 241, the X-axis gradient coil 241 may generatethe gradient magnetic field in the X-axis direction and the generatedgradient magnetic field may change a phase and a frequency of the atomicnucleus or a combination thereof.

FIG. 2B is a diagram illustrating the Y-axis gradient coil 243 accordingto an embodiment of the present disclosure. When the current flows inthe Y-axis gradient coil 243, the Y-axis gradient coil 243 may generatethe gradient magnetic field in the Y-axis direction and the generatedgradient magnetic field may change the phase and the frequency of theatomic nucleus or the combination thereof

FIG. 2C is a diagram illustrating the Z-axis gradient coil 245 accordingto an embodiment of the present disclosure. When the current flows inthe Z-axis gradient coil 245, the Z-axis gradient coil 245 may generatethe gradient magnetic field in the Z-axis direction and the generatedgradient magnetic field may change the phase and the frequency of theatomic nucleus or the combination thereof.

The Z-axis gradient coil 245 according to the embodiment of the presentdisclosure may include a plurality of coils. For example, the gradientcoil 24 may include a plurality of coils having a loop shape. In thiscase, the plurality of coils may be grouped into a plurality of coilgroups and the magnetic resonance imaging system may control theplurality of coils by the unit of the group.

Further, the plurality of coils may be grouped into a plurality of paircoil groups and the magnetic resonance imaging system may control theplurality of coils by the unit of the pair coil group.

FIG. 3 is a diagram for describing a Z-axis gradient coil according toan embodiment of the present disclosure.

The Z-axis gradient coil 245 according to the embodiment of the presentdisclosure may receive the current from the gradient amplifier 32.

According to the embodiment of the present disclosure, the gradientamplifier 32 applies various currents to the Z-axis gradient coil 245under the control of the gradient magnetic field control unit 54 togenerate gradient magnetic fields having various strengths anddirections. For example, the gradient amplifier 32 applies the currentto the Z-axis gradient coil 245 to control at least one of a shape ofthe gradient magnetic field, the strength of the gradient magneticfield, and a slew rate of the gradient magnetic field generated by thecoil group.

In this case, the gradient amplifier 32 may apply the current to theZ-axis gradient coil 245 by the unit of the coil group. For example, thegradient amplifier 32 may control at least one of the shape of thegradient magnetic field, the strength of the gradient magnetic field,and the slew rate of the gradient magnetic field by the unit of the coilgroup by applying the current to the coil group by the unit of thegroup.

The gradient amplifier 32 may control the gradient magnetic field coil24 so as for the gradient magnetic field coil 24 to generate thegradient magnetic field under the control of the gradient magnetic fieldcontrol unit 54. In this case, the gradient amplifier 32 may control thegradient magnetic field coil 24 according to a predetermined program.

The Z-axis gradient coil 245 according to the embodiment of the presentdisclosure may include a plurality of coils. For example, the gradientcoil 24 may include a plurality of coils having a loop shape.

In this case, the plurality of coils may be grouped into a plurality ofcoil groups according to the positions of the coils. For example, two ormore coils adjacent to each other may be grouped so that the pluralityof coils may be grouped. One coil group may include one coil and mayinclude the plurality of coils, but is not limited thereto.

The magnetic resonance imaging system may control the plurality of coilsby the unit of the group. For example, current having the same magnitudemay flow in the coils included in the coil group. Further, current inthe same direction may flow on the coils included in the coil group. Inaddition, current which flows in the coils included in a first coilgroup and current which flows in the coils included in the second coilgroup may be different in at least one of the magnitude and thedirection.

The plurality of coil groups may be grouped into a plurality of paircoil groups. The pair coil group may be configured by a group of coilgroups in which the current of the same magnitude flows and the currentflows in an opposite direction among the plurality of coil groups.

For example, the first coil group 2451 and the second coil group 2452among the plurality of coil groups may be grouped into the pair coilgroup. In this case, the direction of the current flowing in the firstcoil group 2451 and the direction of the current flowing in the secondcoil group may be opposite directions. Further, the magnitude of thecurrent flowing in the first coil group 2451 and the magnitude of thecurrent flowing in the second coil group may be the same as each other.

The Z-axis gradient coil 245 may include a plurality of pair coilgroups. For example, the Z-axis gradient coil 24 may include three paircoil groups, but is not limited thereto.

According to the embodiment of the present disclosure, the magnitude ofthe current flowing in the coils included in the Z-axis gradient coil245 may be controlled by the unit of the pair coil group. For example,current having the same magnitude may flow on the coils included in thesame pair coil group. Further, the magnitude of the current flowing inthe coils included in the first pair coil group 2457 and the magnitudeof the current flowing in the coils included in the second pair coilgroup 2458 may be different from each other.

According to the embodiment of the present disclosure, the coilsincluded in the coil group may be arranged at uniform intervals. Forexample, an interval between a first coil and a second coil included inthe first coil group 2451 may be the same as the interval between thesecond coil and a third coil included in the first coil group 2451.

According to another embodiment of the present disclosure, the coilsincluded in the pair coil group may be arranged at uniform intervals.For example, the interval between the first coil and the second coil ofthe first coil group 2451 included in the first pair coil group 2457 maybe the same as the interval between the third coil and a fourth coil ofthe second coil group 2452 included in the first pair coil group 2457.

According to another embodiment of the present disclosure, all of thecoils included in the coil group may be arranged at uniform intervals.For example, the intervals between the coils included in the pluralityof coil groups may all be the same. For example, the interval betweenthe coils included in the first coil group 2451, the interval betweenthe coils included in the second coil group 2452, the interval betweenthe coils included in a third coil group 2453, the interval between thecoils included in a fourth coil group 2454, the interval between thecoils included in the fifth coil group 2455, and the interval betweenthe coils included in the sixth coil group 2456 may be all the same.

In this case, the interval between adjacent coil groups may be differentfrom the interval between the coils. For example, the interval betweenthe third coil group 2453 adjacent to the first coil group 2451 and thefirst coil group 2451 may be different from the interval between thecoils included in the first coil group 2451.

According to the embodiment of the present disclosure, the coil groupsincluded in the pair coil group may be arranged according to thepositions of other coil groups included in the pair coil group.

For example, another coil group included in the same pair coil group asthe first coil group on a left side may be located first on a right sideamong the coil groups. Further, another coil group included in the samepair coil group as the second coil group on the left side may be locatedsecond on the right side among the coil groups. In addition, anothercoil group included in the same pair coil group as the third coil groupon the left side may be located third on the right side among the coilgroups.

According to the embodiment of the present disclosure, the magneticresonance imaging system 100 may generate various gradient magneticfields by controlling the coils included in the Z-axis gradient coil 245by the unit of the group. For example, the magnetic resonance imagingsystem 100 may generate a linear gradient magnetic field and generate anon-linear gradient magnetic field by controlling the coils included inthe Z-axis gradient coil 245 by the unit of the group, but is notlimited thereto.

Further, the magnetic resonance imaging system 100 may variously changethe strength of the gradient magnetic field formed at a bore bycontrolling the coils included in the Z-axis gradient coil 245 by theunit of the group. For example, the magnetic resonance imaging system100 may generate a gradient magnetic field having the larger strength ina specific part than the gradient magnetic fields in other parts bycontrolling the coils included in the gradient coil 24 by the unit ofthe group.

The magnetic resonance imaging system 100 may variously control theintensity and the strength of the gradient magnetic field formed at thebore by variously controlling the coils included in the Z-axis gradientcoil 245 by the unit of the group.

According to the embodiment of the present disclosure, the Z-axisgradient magnetic field coil 245 may generate at least one of an X-axisgradient magnetic field, a Y-axis gradient magnetic field, and a Z-axisgradient magnetic field. For example, the gradient amplifier 32 maygenerate at least one of the X-axis gradient magnetic field, the Y-axisgradient magnetic field, and the Z-axis gradient magnetic field byapplying various current to the Z-axis gradient magnetic field coil 245.

According to another embodiment of the present disclosure, a structureand a function of the Z-axis gradient magnetic field coil 245 may beapplied to at least one of the X-axis gradient magnetic field coil 241and the Y-axis gradient magnetic field coil 243. As a result, at leastone of the X-axis gradient magnetic field coil 241 and the Y-axisgradient magnetic field coil 243 may generate various gradient magneticfields.

FIG. 4 is a diagram for describing the gradient amplifier according toan embodiment of the present disclosure.

According to the embodiment of the present disclosure, the gradientamplifier 32 may include a plurality of sub gradient amplifiers. Forexample, the gradient amplifier 32 means a group of the sub gradientamplifier and the sub gradient amplifier may amplify the current toapply the amplified current to the gradient coil 24.

According to the embodiment of the present disclosure, the sub gradientamplifier may match the coil group included in the Z-axis gradient coil245. For example, one sub gradient amplifier may match one coil group.In this case, the sub gradient amplifier may amplify the current andapply the amplified current to the coil group. The coil groups may beindependently driven by a plurality of sub gradient amplifiers,respectively.

For example, a first sub gradient amplifier 321 may match the first coilgroup 2451. The first sub gradient amplifier 321 may apply currenthaving the same magnitude and the same direction to at least one coilincluded in the first coil group 2451. Further, a second sub gradientamplifier 322 may match the second coil group 2452 and the second subgradient amplifier 322 may apply current having the same magnitude andthe same direction to at least one coil included in the second coilgroup 2452.

In this case, the magnitude of the current applied to the first coilgroup 2451 may be different from the magnitude of the current applied tothe second coil group 2452. Further, the direction of the currentapplied to the first coil group 2451 may be different from the directionof the current applied to the second coil group 2452 and the magnitudeand the direction of the current applied to the first coil group 2451may be different from the magnitude and the direction of the currentapplied to the second coil group 2452 and the present disclosure is notlimited thereto.

For example, the first sub gradient amplifier 321 may applyfirst-direction current to the first coil group 2451. Further, thesecond sub gradient amplifier 322 may apply second-direction current tothe second coil group 2452. In this case, the first sub gradientamplifier 321 and the second sub gradient amplifier 322 apply currentshaving the same magnitude, respectively to generate the gradientmagnetic field.

FIG. 5 is a diagram for describing a gradient amplifier according toanother embodiment of the present disclosure.

According to the embodiment of the present disclosure, the gradientamplifier 32 may include a plurality of sub gradient amplifiers. Forexample, the gradient amplifier 32 means a group of the sub gradientamplifiers and the sub gradient amplifiers may amplify the current toapply the amplified current to the gradient coil 24.

According to the embodiment of the present disclosure, the sub gradientamplifier may match the pair coil group included in the Z-axis gradientcoil 245. For example, one sub gradient amplifier may match one paircoil group. In this case, the sub gradient amplifier may amplify thecurrent and apply the amplified current to the pair coil group. The paircoil groups may be independently driven by a plurality of sub gradientamplifiers, respectively.

For example, the first sub gradient amplifier 321 may match the firstpair coil group 2457. The first sub gradient amplifier 321 may applycurrent having the same magnitude to the plurality of coils included inthe first pair coil group 2457. Further, the second sub gradientamplifier 322 may match the second pair coil group 2458 and the secondsub gradient amplifier 322 may apply current having the same magnitudeto the plurality of coils included in the second pair coil group 2458.

In this case, the magnitude of the current applied to the first paircoil group 2457 may be different from the magnitude of the currentapplied to the second pair coil group 2458.

According to the embodiment of the present disclosure, the first subgradient amplifier 321 may apply first-direction current to the firstcoil group 2451 included in the first pair coil group 2457. Further, thefirst sub gradient amplifier 321 applies current in a direction oppositeto a first direction to the second coil group 2452 included in the firstpair coil group 2457 to generate the gradient magnetic field.

According to the embodiment of the present disclosure, the first subgradient amplifier 321 applies current to both the first coil group 2451and the second coil group 2452 to generate the gradient magnetic field.

FIG. 6 is a circuit diagram for describing the gradient amplifieraccording to an embodiment of the present disclosure.

According to the embodiment of the present disclosure, the gradientamplifier 32 may be implemented according to the circuit diagram of FIG.6. In addition, the gradient amplifier 32 may include a plurality of subgradient amplifiers and in this case, each sub gradient amplifier may beimplemented according to the circuit diagram of FIG. 6, but is notlimited thereto.

Referring to FIG. 6, the gradient amplifier 32 may include at least oneMOSFET. For example, the gradient amplifier 32 may include at least oneN-channel MOSFET, but is not limited thereto.

According to the embodiment of the present disclosure, the gradientamplifier 32 may include an H-bridge circuit. In this case, the H-bridgecircuit may be implemented with at least one MOSFET. In addition, thegradient amplifier 32 may include a boot strap circuit. In this case,the boot strap circuit may be implemented with at least one diode and atleast one capacitor. In this case, the boot strap circuit may be used tomaintain a high-voltage level.

According to the embodiment of the present disclosure, a magneticresonance circuit system may include a gradient magnetic fieldgeneration module. The gradient magnetic field generation module means amodule which generates the gradient magnetic field to form the gradientmagnetic field. The gradient magnetic field generation module mayinclude the gradient amplifier 32 and the gradient magnetic field coil24.

The gradient amplifier 32 may apply the current to the gradient magneticfield coil 24 under the control of the gradient magnetic field controlunit 54. In this case, the gradient amplifier 32 may supply the currentto the gradient magnetic field coil 24 for a predetermined time and stopsupplying the current when the predetermined time has elapsed.

According to the embodiment of the present disclosure, the gradientamplifier 32 applies various currents to the coil group under thecontrol of the gradient magnetic field control unit 54 to generategradient magnetic fields having various magnitudes and directions. Forexample, the gradient amplifier 32 applies the current to the coil groupto control at least one of a shape of the gradient magnetic field, thestrength of the gradient magnetic field, and a slew rate of the gradientmagnetic field generated by the coil group.

The aforementioned description of the present disclosure is used forexemplification, and it can be understood by those skilled in the artthat the present disclosure can be easily modified in other detailedforms without changing the technical spirit or requisite features of thepresent disclosure. Therefore, it should be appreciated that theaforementioned embodiments are illustrative in all aspects and are notrestricted. For example, respective constituent elements described assingle types can be distributed and implemented, and similarly,constituent elements described to be distributed can also be implementedin a coupled form.

The scope of the present disclosure is represented by claims to bedescribed below rather than the detailed description, and it is to beinterpreted that the meaning and scope of the claims and all the changesor modified forms derived from the equivalents thereof come within thescope of the present disclosure.

Related contents in the best mode for carrying out the presentdisclosure are described as above.

The present disclosure relates to a gradient magnetic field generationmodule and may be used in a magnetic resonance imaging system.

What is claimed is:
 1. A gradient magnetic field generation modulecomprising: a gradient coil formed inside a main magnet and generating agradient magnetic field and including a plurality of coils; and agradient amplifier controlling at least one of a shape of the gradientmagnetic field, a strength of the gradient magnetic field, and a slewrate of the gradient magnetic field generated by the gradient coil,wherein the plurality of coils is grouped into a plurality of coilgroups and current which flows in the plurality of coils isindependently controlled by the unit of a group.
 2. The gradientmagnetic field generation module of claim 1, wherein a first core groupand a second core group among the plurality of coil groups are groupedinto a pair coil group, and a direction of current which flows in thefirst coil group and a direction of current which flows in the secondcoil group are opposite directions.
 3. The gradient magnetic fieldgeneration module of claim 1, wherein the plurality of coil groups isgrouped into a plurality of pair coil groups and magnitudes of thecurrent which flows in the plurality of pair coil groups, respectivelyare different from each other.
 4. The gradient magnetic field generationmodule of claim 1, wherein the gradient coil generates at least one ofan X-axis gradient magnetic field, a Y-axis gradient magnetic field, anda Z-axis gradient magnetic field.
 5. The gradient magnetic fieldgeneration module of claim 1, wherein the gradient amplifierindependently controls each of the plurality of coil groups toindependently control a shape, a strength, and a slew rate of thegradient magnetic field generated by each of the plurality of coilgroups.
 6. The gradient magnetic field generation module of claim 1,wherein two or more coils adjacent to each other are grouped into agroup the plurality of coils.